This invention relates to the manufacture of halogenated alkanes using the catalytic reaction of haloalkanes with halogenated olefins, compounds produced thereby, azeotropic compositions which can be obtained upon fluorination of such compounds, and use of azeotropes in separation processes.
The catalyzed radical addition of haloalkanes to olefins is a well known reaction. Typically, however, when a haloalkane (e.g., AB, where A is a substituted carbon atom and B is a halogen other than fluorine) is added to an olefin (e.g., CH2xe2x95x90CHR) to form the saturated adduct (e.g., CH2ACHBR), the products (i.e., halogenated addition compounds) also include varying amounts of telomers (e.g., A(CH2CHR)nB, where n is equal to 2 or more). For example, Canadian Patent No. 2,073,533 discloses a process for the manufacture of CCl3CH2CCl3 by reacting carbon tetrachloride with vinylidene chloride using copper catalysts in acetonitrile. The selectivity for CCl3CH2CCl3 with respect to converted vinylidene chloride was 87%. It has been shown in the art that the major by-product is the C5 telomer, CCl3(CH2CCl2)2Cl. Furthermore, since the catalyzed addition of haloalkanes to olefins is done in a homogeneous medium, separation of the catalyst from the product can present difficulties. This is especially so when it is desired to run the reaction in a continuous manner.
The halogenated adducts are useful intermediates for the production of fluoroalkanes, particularly, hydrofluoroalkanes. These latter compounds are useful as refrigerants, fire extinguishants, heat transfer media, propellants, foaming agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, displacement drying agents and power cycle working fluids. There is an interest in developing more efficient processes for the manufacture of hydrofluoroalkanes.
A liquid phase process is provided in accordance with this invention for producing halogenated alkane adducts of the formula CAR1R2CBR3R4 wherein R1, R2, R3, and R4 are each independently selected from the group consisting of H, Br, Cl, F, C1-C6 alkyl, CN, CO2CH3, CH2Cl, and aryl (e.g., phenyl), provided that when either R3 or R4 is selected from the group consisting of C3-C6 alkyl, CN, CO2CH3, CH2Cl, and aryl, then R1, R2, and the other of R3 and R4 are H, and when R3 and R4 are selected from the group consisting of Cl, F, CH3 and C2H5, then R1 and R2 are H, and when either R1 or R2 and either R3 or R4 are selected from the group consisting of Cl, F, CH3 and C2H5, then the other of R1 and R2 and the other of R3 and R4 are H: A is selected from the group consisting of CX3, CH3xe2x88x92aXa, CnH(2n+1)xe2x88x92bXb and CHcX2xe2x88x92cR, where R is CnH(2n+1)xe2x88x92bXb (e.g., CF3 and CCl2CF3), each X is independently selected from the group consisting of Br, F, Cl and I, a is an integer from 0 to 3, n is an integer from 1 to 6, b is an integer from 1 to 2n+1, and c is an integer from 0 to 1; and B is selected from the group consisting of Br, Cl and I; provided that (1) when A is CX3 then only one of X is I, (2) when A is CH3xe2x88x92aXa, then each X is B and a is 2 when B is Br or Cl, and a is an integer from 0 to 2 when B is I, and (3) when A is CnH(2n+1)xe2x88x92bXb, then each X is independently selected from Cl and F, and B is I. The process comprises contacting a halogenated alkane of the formula AB (where A and B are as indicated above) with an olefin of the formula CR1R2xe2x95x90CR3R4 (where R1, R2, R3 and R4 are as indicated above) in a dinitrile or cyclic carbonate ester solvent which divides the reaction mixture into two liquid phases and in the presence of a catalyst system containing (i) at least one catalyst selected from the group consisting of monovalent and divalent copper; and optionally (ii) a promoter selected from the group consisting of aromatic or aliphatic heterocyclic compounds which contain at least one carbon-nitrogen double bond in the heterocyclic ring.
This invention further provides a process for producing hydrofluoroalkanes (e.g., CF3CH2CHF2). This process comprises (a) producing a halogenated alkane adduct (e.g., CCl3CH2CHCl2) by reacting AB (e.g., CCl4) and CR1R2xe2x95x90CR3R4 (e.g., CH2xe2x95x90CHCl) as indicated above (provided that R1, R2, R3 and R4 are independently selected from H, CH3, C2H5, Cl and F, B and X are Cl and at least one of AB and CR1R2xe2x95x90CR3R4 contains hydrogen), and (b) reacting the adduct produced in (a) with HF.
This invention also provides a process for the purification of at least one compound of the formula CA1R5R6CB1R7R8 from a mixture comprising HF and said at least one compound, wherein A1 is selected from the group consisting of CH3xe2x88x92aX1a and CHcX12xe2x88x92cR9 where R9 is CnH(2n+1)xe2x88x92bXb, each X1 and B1 is independently selected from the group consisting of Cl and F, R5, R6, R7, and R8 are each independently selected from the group consisting of H, Cl and F, and a, b, c and n are as defined above, provided that at least one of A1, R5, R6, R7, or R8 comprises hydrogen. The purification process comprises (a) subjecting the mixture of HF and said at least one compound to a distillation step in which a composition enriched in either (i) HF or (ii) said at least one compound is removed as a first distillate with the bottoms being enriched in the other of said components (i) or (ii); (b) subjecting said first distillate to an additional distillation conducted at a different pressure in which the component enriched as bottoms in (a) is removed as a second distillate with the bottoms of the additional distillation enriched in the component enriched in the first distillate; and (c) recovering at least one compound of the formula CA1R5R6CB1R7R8 essentially free of HF as bottoms from either the distillation of (a) or the distillation of (b).
New compounds provided in accordance with this invention include CF3CF2CCl2CH2Cl3, CF3CCl2CH2CH2Cl and CF3CCl2CH2CHClF. These compounds are useful as intermediates for producing hydrofluorocarbons.
New compositions produced by this invention include azeotropic compositions of CF3CH2CHF2 with HF and azeotropic compositions of CF3CH2CClF2 with HF. A composition comprising from about 44 to 84 mole percent HF and from about 56 to 16 mole percent CF3CH2CHF2 is provided which, when the temperature is adjusted within the range of xe2x88x9250xc2x0 C. to 130xc2x0 C., exhibits a relative volatility of about 1 at a pressure within the range of 5.5 kPa to 3850 kPa. Also, a composition comprising from about 63.0 to 90.1 mole percent HF and from about 37.0 to 9.9 mole percent CF3CH2CClF2 is provided which, when the temperature is adjusted within the range of xe2x88x9240xc2x0 C. to 110xc2x0 C., exhibits a relative volatility of about 1 at a pressure within the range of about 9.3 kPa to 2194 kPa.